1. Field of the Invention
This invention relates to devices which interlock circuit breakers to preclude two circuits from being closed simultaneously. Specifically, this invention relates to a slidable interlock device positioned between two circuit breakers which are mounted horizontally and oriented so that the closed position of each circuit breaker handle is proximal to the other circuit breaker.
2. Background Information
There are a number of applications where it is required that the operation of two circuit breakers be coordinated such that only one circuit breaker can be in the closed, operating position at one time. One such application is providing a power-consuming load with electrical power from either of two different sources, such as a commercial power system and an auxiliary supply. It is imperative in such applications that only one circuit breaker be in the closed, operating position at one time.
U.S. Pat. No. 4,286,242 discloses an interlock utilizing plungers which engage the internal operating mechanisms of the circuit breaker. In this interlock, which is designed for use with SPB type circuit breakers, the plunger of a first circuit breaker to be closed, engages a lever on a rod to rotate the rod about its axis. Another lever on the other end of the rod engages a push rod which holds the second circuit breaker in the trip-free condition. An identical mechanism engaged when the second breaker is closed, holds the first circuit breaker in the trip-free condition. Thus, two complete mechanisms are required so that any attempt to close one circuit breaker while the other is closed, returns the open circuit breaker to the trip-free condition.
Other interlocks are known which couple the actuating means, for example, operating handles, of circuit breakers whose operation is to be coordinated. Typically, the circuit breakers and the type of actuating means employed by the circuit breakers are similar if not identical. For example U.S. Pat. No. 5,397,868 discloses a transfer switch for a pair of circuit breakers. As disclosed, the circuit breakers are mounted vertically, each breaker having an actuating handle traveling between an upper, closed position and a lower, open position. The transfer switch ensures that only one actuating handle may be in the upper, closed position at one time.
As disclosed in U.S. Pat. No. 5,397, 868, circuit breakers for industrial applications are typically mounted in a vertical relation to each other. In this configuration the closed, operating position of each circuit breaker is traditionally when the circuit breaker actuating handle is in the higher position. This configuration requires more space than a circuit breaker panel where the circuit breakers are aligned horizontally adjacent to each other with the closed, operating position of the circuit breaker handle being proximal to the center line between the pairs of circuit breakers. Interlock devices are typically limited to working with circuit breakers that have their operating position in the same direction.
One common circuit breaker configuration has a rectangular body and a pivoting, actuating handle mounted medially thereon. The actuating handle travels in a direction parallel to the longer sides of the rectangular circuit breaker body. As such, when circuit breakers are mounted in pairs, with the switches operating in the vertical direction (typically with the upward position being the closed, operating position), the circuit breakers will require more room than circuit breakers which are mounted so that the switches travel in the horizontal direction. To save space in circuit breaker panels, it is not uncommon to mount rectangular circuit breaker pairs with their longer sides running horizontally. When oriented in this manner, the operating switches travel in an arcuate path in the horizontal plane, where the closed position is toward the other circuit breaker. Unlike vertically mounted circuit breaker pairs, the closed position of each circuit breaker is in the opposite direction of the other circuit breaker in the pair. That is, a pair of circuit breakers, one laying on the left of the center line and one laying on the right of the center line, each have actuating switches which are operable in the opposite direction from each other i.e., the left circuit breaker will be operable when the actuating handle is in the right position whereas, the right circuit breaker will be operable when the actuating handle is in the left position.
Because circuit breaker interlock devices in the prior art are designed to prevent circuit breaker actuating handles from being disposed in the same direction simultaneously, there is a need for an interlock device which will prevent the actuating handles of a horizontally mounted circuit breaker pair, which are oriented so that the actuating handles are in the closed, operating position when the circuit breaker actuating handle is proximal to the other circuit breaker, from being in the closed, operating position simultaneously.
There is also a need for an interlock device which may be utilized with existing circuit breaker designs with minimal or no modifications to the existing circuit breakers.
There is also a need for an interlock device which may be used with either one-pole circuit breakers, two-pole circuit breakers or three-pole circuit breakers.